In recent years, more and more goods are being shipped and transported by ship, aircraft, truck, train, etc. This tendency has become accelerated due to several factors which include increases in distances between the producers; the "just in time" manufacturing techniques where inventories are limited and producers accept goods only when they are necessary; and increased affluence of many people all over the world who can now afford to purchase and consume more. This trend has caused large demands to be placed upon the transportation industry. It is now highly desirable to provide more efficient transportation techniques.
One nemesis of effective cargo transportation is misplacing cargo. The time required to search for the misplaced cargo not only consumes valuable manpower, but also can cause the cargo to spoil or become obsolete. The balance between providing effective transportation of large quantities of goods and guarding against misplacing considerable amounts of goods is often quite delicate.
One efficient technique used to store containers such as shipping containers within a limited space is nesting containers (where a plurality of smaller containers fit within one larger container.) Unfortunately, it is quite easy to forget the location of nested goods, and the shipper is uncertain of which larger container some cargo is stored in. Nesting requires an efficient inventory system to be able to relocate cargo. Providing an inventory list of all of the cargo stored in all of the containers for larger volume nesting applications requires considerable time to compile, is very tedious to produce, and is often very difficult or unreliable to use efficiently.
Another technique to efficiently store cargo is stacking. Stacking is optimally utilized when the containers are of similar size and shape, and are configured to permit stacking. When large amounts of cargo are stacked, prior art techniques require considerable inventory logs to recall where each container is stacked. In such applications as container or cargo ships (where there are a large number of containers stacked in each column, there are a large number of columns in each ship, and the cargo appears very similar) the task of recalling inventory becomes especially challenging.
A tool which has proven itself useful in many applications of locating objects is electronic tagging. Each electronic tag is capable of containing inventory information. Electronic tags in the past have been applied only to individual items, with no interaction between the tags. When a plurality of items containing such electronic tags are arranged in close proximity, it becomes very difficult to precisely position each electronic tag (and the cargo associated therewith) with respect to other containers in which it is nested or stacked such that the precise location of the stored object associated with the electronic tag could be determined. Additionally, some containers provide a barrier between certain electronic tags and a hand-held unit which is used to locate the container which the tag is affixed to. This barrier may block one or more of the transmitted signals, thereby making precise locating of a specific cargo container (or some inventoried contents located therein) very difficult.
Another difficulty is that when inventoried cargo is restacked and/or renested, the relative positions of the cargo changes. Maintaining a manual inventory list in its latest configuration as certain cargo is restacked or renested becomes a considerable challenge, which leads to potential error and confusion.
It would be desirable to provide some system which precisely locates, or at least is able to gain access to some precise positional information, when an electronic tag is affixed to a cargo container which is stored in a nested or stacked configuration. This precise positional information should be able to be updated automatically when the cargo is restacked or renested.